Winter Forage Cover Crop Trials

Bruce Munda,
Tim C. Knowles,
Art Meen
Vic Wakimoto
and
Bill Worthy

Abstract

Several crops were evaluated at Worthy farms, near
Marana, AZ, Wakimoto farms, Mohave Valley, near Bullhead
City, AZ, and the Tucson Plant Materials Center for use
as a winter cover crop following cotton with potential to
reduce wind erosion and produce one to two hay cuttings.
Hairy vetch (Vicia villosa), 'Lana' woolypod vetch (Vicia
villosa ssp. varia), 'Papago' pea (Pisum sativum), and
'Biomaster' pea (Pisum sativum) were sown at the Tucson
Plant Materials Center. Species sown at Worthy farm were:
Papago pea, Lana vetch, and Biomaster pea. Species sown
at Wakimoto farm were: Biomaster pea, Lana vetch, 'Seco'
barley (Hordeum vulgare), and 'Multi-cut' berseem clover
(Trifolium alexandrinum). Forage yield varied between
locations due to sowning date, number of irrigations, and
soil textures. Biomaster pea, Papago pea, and Lana vetch
performed well at all three locations. However, Biomaster
yields were more consistent and due to its shorter
growing season may be the better choice as a winter cover
between cotton crops. Additional trials are scheduled for
the fall of 1998.

Introduction

Soil improvement benefits from leguminous cover crops
are well documented. However, traditional southwestern
cotton farming practices have not utilized cover crops
for a number of reasons including increased production
costs and the lack of a productive, high forage quality,
short season legume. Blowing dust and potential PM-10
violations are growing concerns in many of the cotton
producing areas in Arizona. Mohave Valley experiences its
highest wind velocities and lowest rainfall from December
to February which coincides with the fallow period
between cotton crops. Winter cover crops, which could
provide a profitable hay crop, have been suggested as a
best management practice to reduce fugitive dust
emissions. Also, some growers are becoming interested in
growing cotton organically. Cover crops that will supply
nitrogen and fit the time available between cotton crops
need to be identified and evaluated. The objectives of
these trials were to evaluate various winter cover crops
for forage production, forage quality as hay for the
horse or dairy cows market, and their suitability as a
cover crop following cotton.

Seco barley is a water efficient "one irrigation
barley" grown for forage, grain, and as a cover crop
in south central Arizona. Multi-cut berseem clover has
been grown as a fall sown winter hay crop in California
deserts and can produce 10-12 tons of high quality hay in
8 cuttings during the period from 1 Dec through July when
sown by October. Biomaster pea is a winter forage with
high nutritive quality, is well adapted to climates with
mild winters, and becomes quickly established. Lana
woolypod vetch is commonly grown as a green manure crop
and its spreading, viney growth habit provides a fast
ground cover. Hairy vetch is used in the eastern United
States as a fall sown green manure crop for summer
vegetables.

Materials and Methods

Trials were conducted at the Tucson Plant Materials
Center (PMC), Tucson, AZ, Bill Worthy farms, Marana, AZ
and Victor Wakimoto farms on the Fort Mohave Indian
Reservation near Bullhead City, AZ. The Marana and Fort
Mohave Indian Reservation trials were sown following the
1997 cotton crop. Soils at these sites were listed as
highly erodible land (HEL). On HEL soils it is desirable
to maintain an adequate cover during the winter and
spring months to reduce wind erosion.

Traits evaluated included: height, formation of
nitrogen fixing nodules, stand, and biomass production.
Species planted at the PMC were: hairy vetch , Lana
vetch, Papago pea, and Biomaster pea. Species planted at
Worthy farms were: Papago pea, Lana vetch, and Biomaster
pea. Species planted at the Wakimoto farms were:
Biomaster pea, Lana vetch, Seco barley, and Berseem
clover. A Rhizobium inoculant was added to all
species except Seco barley. A sticking agent was used to
ensure a good bacteria coating on the seed. Multi-cut
berseem clover was pre-inoculated, coated, by the seed
vendor.

At the PMC, crops were sown on 03-05 Nov. 1997 in four
borders totaling 1.0 acres for each species except hairy
vetch which was sown in two borders totaling 0.5 acres.
All species were drill seeded at 70-80 lb/A at a depth of
0.5-1.0 inches. One irrigation was applied following
planting. Soils are Anthony loamy fine sand and Comoro
fine sandy loam. Plantings did not receive supplemental
fertilization.

At Worthy farms, crops were sown on 01 Jan 1998. Each
species was planted in two-acre blocks at 75-80 lb/A at a
depth of 0.5-1.0 inches. Sowing was delayed due to a late
cotton harvest and heavy precipitation during Dec. 1997.
Soils are Gila sandy loam and Vinton loamy sand. One
irrigation was applied after sowing. This trial received
subsequent irrigations but these were not recorded.
Supplemental fertilizations, if any, were not recorded.

At Wakimoto farms, crops were sown on 25 Dec. 1997
into 6 inch rows. Each forage was planted into one three
acre border. Biomaster pea and Seco barley were each sown
at 75 lb/A at a depth of 0.5-1.0 inches. Lana vetch was
sown at 90 lb/A and 0.5 inches deep. Berseem clover was
sown at a rate of 25 lb/A and 0.5 inches deep. Soils are
Lagunita sand in the south half of the field and
Holtzville silty clay in the north half of the field. Due
to differences in production for each soil type, yield
and quality measurements were conducted for both soil
types. The planting received one irrigation on 02 Jan
1998 with 15 gallons of urea ammonium (UAN32) applied
with the irrigation water. Two hundred pounds of ammonium
phosphate (16-20-0) was broadcast applied and disced in
preplant. Emergence occurred by mid-January for all four
crops.

All clipping measurements were conducted
with a 9.6 ft2 frame. Four frames were clipped
for each species, border, and soil type. Fresh weight was
recorded in grams which allowed for conversion to pounds
per acre by multiplying the fresh weight by 10.

Results and Discussion

At the PMC, 100 days after planting (DAP), stand and
height measurements were taken (Table 1). Height and
fresh weight measurements were made on 14 Apr 1998, 162
DAP, and dry weight measured on 12 May 1998 (Table 1).
Hairy vetch did not initiate vigorous growth until late
March, allowing a good stand of mustard to establish.
Flowering did not begin until 13 April. Nodules were
found but they were few and small. Lana vetch had the
highest fresh and dry weight yields among all species
tested at the PMC. Lana vetch covered the ground and
out-competed emerging mustard seedlings. Lana vetch
initiated flowering on 15 Mar and finished flowering the
end of April. On 13 Apr, Lana vetch plants had numerous
small nodules. These grew well through the spring and
matured in mid-May. Papago pea had the second highest
fresh weight yield. Plants grew well throughout the
season and competed well with mustard especially where
the stand was uniform and thick. Papago pea began
flowering on 23 Feb and finished flowering on 27 April.
Nodules were abundant with many measuring 1/2 inch in
diameter. Plants had matured by mid-May. Biomaster pea
initiated flowering on 23 Feb. This variety had the
largest nodules of all the species with some nodules
measuring 1 inch in diameter. Nodules were common in the
upper 2-3 inches of the soil but were found as deep as 6
inches. Biomaster pea had the shortest growing season
with fruit set by 13 April and matured plants by the end
of April.

At Worthy farms on 2 Mar, 46 DAP, stand and height
measurements were taken (Table 2). These plots were not
clipped until 13 May, 118 DAP. At this time all of the
species had matured. Due to warm temperatures in May, the
soilĖs low water holding capacity, and infrequent
irrigations, biomass yields were low (Table 2). Plant
height measurements were not taken. Biomaster pea
performed best in terms of yield, followed by Lana vetch
and Papago pea. However, the Biomaster pea was planted
close to an existing wheat crop and probably benefited
from excess irrigation water. Nodules were found on all
species but were smaller and not as numerous as those
found at the PMC.

At Wakimoto farms on 19 Feb, 50 DAP, height and stand
density was measured (Table 3). Height and yield
measurements were taken on 26 Mar, 91 DAP, (Table 4).
Forage quality, for all crops, was measured on 11 Mar
1998 for both soil types (Table 5). Only one cutting was
possible for the production period going from 25 Dec
through 26 Mar for all four forages. Spring forage yields
were poor during the short production period for berseem
clover sown on either soil and Biomaster pea sown on the
silty clay soil. Highest forage yields resulted from
sowing Biomaster pea or Lana vetch on the sandy soil and
Seco barley or Multi-cut berseem clover on the silty clay
soil (Table 4). Multi-cut berseem clover was slow growing
and produced low tonnage and relatively lower quality
hay, compared to the other forage crops. This was due to
the late planting date which resulted in very slow
establishment. Lana vetch produced ample tonnage and good
quality hay but due to its low, spreading, growth habit
it was too short to cut for hay with a mechanical
harvester or swather. However, it provided a fast ground
cover and would make an excellent green manure crop with
its relatively high tonnage and very high nitrogen
content. Seco barley was also a fast growing ground cover
and produced high tonnage compared to the other forages.
However, it had a relatively poor hay quality. Grown
under the conditions of this study, it would be a good
choice for a residue/ erosion control crop. Biomaster pea
had relatively high hay tonnage, high protein levels, and
low acid detergent fiber levels, compared to the other
forages grown in this study. It was not harvested
mechanically for hay, but seemed to cure well enough to
put up an acceptable bale. Nodules were found on the all
of the legumes with Biomaster pea having the largest at
approximately 1/4 inch in diameter.

In summary, Biomaster pea, Lana vetch, and Papago pea
have potential as winter cover crops. Biomaster pea, due
to its shorter growing season, may be the best suited
variety. Forage yield potentials for the above crops will
be reevaluated during 1998-99.

Acknowledgments

Appreciation is extended to Bill Worthy Farms and
Victor Wakimoto Farms for their efforts in conducting
these trials.